Doctors disagree whether a lower level of salt consumed by the general population would result in fewer cases of high blood pressure.
Yes. We can prevent hypertension and make a big dent in hypertension- related disease and death by lowering salt consumption as a society. I base this conclusion on a vast array of data, including the results of Intersalt, a survey of more than 10,000 people in 32 countries that linked higher intake to higher blood pressures and higher pressures with age.
Furthermore, in populations with habitual low salt intakes, average blood pressures were low, there was little or no pressure rise with age and few people -- or none -- had hypertension. These results agree with clinical research on lowering blood pressure by reducing salt intake, with animal data on salt-induced hypertension and with anthropologic evidence indicating that humans are adapted by evolution to a low salt intake.
If Americans were eating an average of 3 grams of salt daily, instead of the current 9 grams, the average systolic pressure -- the pressure of blood against the vessel walls when the heart is contracting -- would, conservatively, be at least 2 millimeters of mercury lower. Long-term prospective population studies indicate that such a reduction translates into a 4 percent lower death rate from coronary disease, a 6 percent lower death rate from stroke and a 3 percent lower death rate from all causes. This means about 12,000 fewer deaths a year in people ages 45 to 64.
Medicine's approach to this vast problem has been late, defensive and reactive: When frank hypertension has developed, then it's treated -- mainly with drugs. This bypasses the third of the adult population with "high-normal" pressures. Relied on as the sole strategy, it means a never-ending problem with each new generation. -- Jeremiah Stamler Dingman Professor of Cardiology, Northwestern University; Principal investigator, Intersalt
No. Evidence is not compelling that lowering salt intake -- especially within a range most people can accept -- will reduce pressure. Studies years ago with the rice diet showed pressures could be lowered, but it's not clear that sodium reduction was what did it. And when patients are put on that sort of draconian diet, few are able to sustain it.
We put 40 mild, non-drug-treated hypertensives on a low-salt diet. We got them as low as we could without special foods, but there was no measurable impact on blood pressure.
Studies aimed at lowering community levels of salt use have been disappointing, too. Studies in Belgium, New Zealand and Portugal showed it's hard to achieve and sustain -- and has no significant effect. Most civilized societies have about the same levels of salt -- around 9 grams -- in their daily diets. To get down to 5 to 6 grams per day without using special foods, a person would have to avoid prepared foods that have sodium preservatives; eat fresh vegetables, fruits and meats and avoid adding extra salt at mealtimes.
To reduce blood pressure, it may be necessary to cut intake even lower, but that would be impossible without a drastic change in someone's lifestyle. The Intersalt study projected significant declines in death rates if society lowered its salt consumption by two thirds. But this prediction, based on the Framingham Heart Study, one of the first long-term measures of a community's population in terms of heart health, only looked at factors related to cardiovascular health without saying whether lowering those factors would produce a benefit. Many things have changed in the past 40 years, so some Framingham data may not give complete explanations for why deaths from stroke and heart disease occur. For example, blood pressure control in itself did not reduce the heart attack rate as much as would have been predicted by the Framingham study. -- Alexander Logan Head of Clinical Epidemiology, Mount Sinai Hospital, Toronto; President, Canadian Hypertension Society
1990, Physician's Weekly, a Whittle Communications Publication; reprinted with permission